The present invention relates to a bus switching structure and a computer using the bus switching structure. More particularly, the invention relates to techniques adapted advantageously to control connection of input/output (I/O) slots for use with Peripheral Component Interconnect (PCI) buses.
Computer systems, such as workstations and servers, increasingly are adopting a dual PCI bus arrangement to address high-speed processing requirements. An aim of implementing such a dual PCI bus arrangement is to distribute the loads evenly on the I/O buses thereof to enhance the performance of the entire computer system. This type of bus arrangement used on local buses in a computer system is discussed and illustrated in detail on pp. 70-71 in "The Latest PC Technologies" (Supplement to Nikkei Byte, a Japanese publication from Nikkei BP Co., Jun. 21, 1994). The publication describes features of the PCI bus.
Investigations and experiments of such bus arrangements led to the discovery of some problems specific to the dual PC bus arrangements intended for I/O bus load distribution. The major problems are as follows:
One problem occurs where each of a plurality of I/O devices is connected fixedly to one of two PCI buses. Thus, either of the PCI buses will tend to be more heavily burdened with loads depending on the frequency of use and duration of use of the particular PCI bus to which the I/O devices are connected then the other PCI bus. The unbalanced loads prevent the computer system from reaching its full potential.
Another problem occurs when, in accordance with actual use conditions, an operator attempts to rearrange the I/O slot connections to the PCI buses so that the two PCI buses will be used in a balanced manner. This, however, requires the operator to have specialized knowledge of computer hardware, particularly the disassembling of the enclosure of the computer system and the rearranging of cable connections. Further, rearranging I/O slot connections to balance the loads on the PCI busses takes time and effort. Worse, an error or mistake made during the rearrangement can disable the computer system or destroy its parts.